A Heterogeneous Multi-Robot System for Autonomous Object Retrieval in
Challenging GNSS-denied Maritime Environment
Abstract
Marine intervention tasks for retrieving large and heavy objects from
vessels at sea is significantly important for maritime security.
However, it remains a challenging task due to the lack of effective
retrieval methods. Harsh open-sea conditions, unreliable GNSS due to
either interruptions or deliberate spoofing by the vessels and the
limitations of single robots in localizing and manipulating these
objects pose significant challenges for the operations. To address these
challenges, this article proposes an autonomous heterogeneous
multi-robot system comprising two UAVs and a 6-DOF robot arm mounted on
a USV to perform this complex task in a GNSS-denied marine environment.
GNSS limitations for UAV localization are addressed using UWB beacons
specially installed on the USV. Our approach involves the robot arm
initially estimating the object’s position. Then the UAVs fly over the
target vessel and search for the object using this information. Once
object is located, a custom-designed tethered bar mechanism attached to
the UAVs drags the object towards the workspace of the robot arm mounted
in the USV. This work also introduces a decentralized framework to
facilitate effective information sharing and collaboration among the
robots. Field trials in maritime conditions demonstrate that by
combining these elements, our system possesses significant potential for
real-world maritime security and rescue applications. Videos for the
field trails can be found at https://youtu.be/a_JzZf7QqWM